Python regex matches but won't sub immediately afterward

Question

I am trying to change settings.py by regex instead of by hand. I have a regex that matches all of installed apps and grabs all except the last paren:

rgx = "(?P<start>INSTALLED_APPS.*?)\)"

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
)
match = re.search(rgx, content, re.DOTALL)

grabs

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',

but for some reason when I go to sub it, with a new app, like

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'my-new-app',
text, n = re.subn(rgx, new_string, content, re.DOTALL)

it doesn't sub anything. I ran as subn and proved it wasn't matching. This makes no sense, because I am using the exact same regex that just made a match. How can I get the exact same regex to match and then not match the exact same string?

Answer 1

您使用re.DOTALL作为count参数。请将其用于flags：

re.subn(rgx, new_string, content, flags=re.DOTALL)